Field of Invention
The present invention relates to a method and an apparatus for controlling an object movement on a screen; particularly, it relates to such method and apparatus capable of adjusting the movement and the positioning of the cursor.
Description of Related Art
Currently, if a user intends to open a file in a computer, he or she usually controls a cursor with a computer input device and clicks an icon corresponding to the file on a computer screen to open it. A mouse is one type of the most often used computer input device. The mouse can control the position of the cursor on the computer screen and select an icon on the screen or trigger a corresponding function represented by the icon by clicking its button. In addition to controlling the cursor by the mouse, the cursor can also be controlled through a touch panel or a writing board. Such computer input devices capable of controlling the movement of the cursor are hereinafter referred as “pointing devices”). To control a cursor, it is required to calculate the position of the cursor. Taking an optical mouse as an example, the conventional approach for calculating the cursor position is to first determine the brightness of the pixels, and then use the pixels whose brightness is larger than a threshold as a basis for calculation. The calculation of the cursor position is carried out by taking the brightness of the pixels as a weighting factor, to obtain the gravity center of the pixels as the position of the cursor.
When controlling the cursor, the user must precisely move the cursor to the desired icon so as to execute the program or open the file. Usually, the resolution of the screen is high; therefore, a high accuracy is required for positioning the cursor, leading to the high resolution requirement of the pointing device. Taking an optical mouse as an example, because the position of the cursor is obtained by calculating the gravity center or centroid of the pixels, wherein the brightness of the pixels is taken into account, the high resolution requirement leads to more complicated calculation. If the pointing device can adopt a structure with low resolution, its cost can accordingly be reduced. However, because of the low resolution, the calculation may not be able to precisely position the cursor. For example, assuming that the ratio of the resolution of the pointing device to that of the screen is 1:8, when the user moves the pointing device by one unit (e.g., in the case that the pointing device is an optical mouse, one unit represents one pixel on the image sensor), the cursor correspondingly moves by eight units (e.g., eight pixels) on the screen. In other words, one unit for the pointing device corresponds to eight units for the screen. Under such circumstance, if the difference between the current position and the position where the user intends to move to is smaller than eight units, the user will be unable to arrive at the desired cursor position no matter how the user move the pointing device back and forth.
In view of the above, to overcome the drawbacks in the prior art, the present invention proposes a method and an apparatus for controlling an object movement on a screen, which is capable of positioning the object on the screen precisely even though the pointing device, as compared with the screen, has a lower resolution. The object on the screen can be, for example but not limited to, the above-mentioned cursor, or any other objects such as roles or equipments in an electronic game.